1. Field of the Invention
The present invention relates to an electron beam apparatus having an electron source for emitting electrons, and used as an image-forming apparatus, and a spacer for internally supporting an enclosure device arranged in the electron beam apparatus, and more particularly to an electron beam apparatus having a surface-conduction electron emitter device working as an electron source, and a spacer.
2. Description of the Related Art
Two types of electrode emitters, a hot-cathode type electron source and cold-cathode type electron source, are known. The cold-cathode type electron sources include a field emission (FE) device, metal/insulator/metal (MIM) device, surface-conduction electron emitter (SCE) device, etc.
The surface-conduction electron emitter device uses the phenomenon that electrons are emitted if a current flows through the surface of a small-sized, thin film formed on a substrate in a direction parallel with the surface of the thin film. Among such surface-conduction electron emitter devices, there is one device proposed by Elinson employing an SnO2 film, and another device proposed by employing an Au thin film, an In2O3/SnO2 thin film, or a carbon thin film.
Since the surface-conduction electron emitter device from among the cold-cathode devices is simple in construction and easy to manufacture, a number of devices can be formed over a wide surface area. The application of the surface-conduction electron emitter device as an image-forming apparatus such as an image display device, or an image recording device, or a charged beam source has been extensively studied.
One application example of the image display apparatus includes a spacer substrate, a faceplate as a second member having a fluorescent material, and a rear plate as a first member having an electron source. The space between the faceplate and the rear plate is maintained in a vacuum.
There is a potential difference between the faceplate and the rear plate with the faceplate set at a potential higher than that of the rear plate. Arranged on the rear plate are an electron emitter that emits electrons, a driving circuit that drives the electron emitter, and wiring electrodes that connect the electron emitter to the driving circuit. When the electron emitter is driven by the wiring electrodes, electrons are emitted from the electron emitter toward the faceplate, and the fluorescent material on the faceplate forms a desired image.
The spacer substrate interposed between the faceplate and the rear plate maintains the gap between the faceplate and the rear plate against the atmospheric pressure. The spacer substrate must have a sufficient mechanical strength to withstand the atmospheric pressure. It is also important to make sure that the spacer substrate does not affect the trajectory of electrons traveling between the rear plate and the faceplate.
The charge accumulated in the spacer substrate greatly affects the trajectory of electrons traveling between the rear plate and the faceplate. Some of the electrons emitted from the electron emitter or electrons reflected off the faceplate enter the spacer substrate, causing secondary electrons to be emitted from the spacer substrate. Also, ions caused as a result of the collision of electrons sticks to the surface of the spacer substrate. As a result, the spacer substrate is charged.
If the spacer substrate is positively charged, electrons flying within a close range therefrom are attracted by the spacer substrate. These electrons are deflected from a trajectory thereof to form a desired image. The resulting image on the faceplate is thus subject to distortion. The attractive force acting on the electrons becomes large as the electrons fly near the spacer substrate. The nearer the electrons are to the spacer substrate, the larger the distortion of the image on the faceplate. In such an image display apparatus, the electron trajectory is deviated more when the electrons reach the faceplate as the spacing between the rear plate and the faceplate is increased. The distortion in the image becomes pronounced.
To control the distortion of the image, an electrode for correcting the electron trajectory is conventionally formed in the spacer substrate, or the spacer substrate is conventionally coated with a resistive film having a high resistance for conduction, thereby allowing a slight current to flow and thereby to remove a charge therefrom.
In another method, spacer electrodes are arranged on the spacer substrate at the contact points thereof with each of the faceplate and the rear plate to apply a uniform electric field to a coating material of the spacer substrate. This arrangement prevents the spacer substrate from being damaged by poor contacts or concentration of current.
As disclosed in Japanese Laid-Open Patent Application No. 2000-311632, the surface of the spacer substrate is ruggedized, and is then coated with a high-resistance material to control the amount of charge in the spacer substrate.
Using the above-mentioned techniques, the conventional electron apparatus controls the electrons traveling close to the spacer from being attracted by the spacer, and corrects the distortion in the image.
A high definition requirement on the image display apparatus is currently mounting, and there is a need for an electron beam apparatus that controls the electron beam with a high accuracy.